A subcellular fraction of lamellar granules of rodent epidermis will be employed to characterize the lipid, protein, and enzyme content of these organelles and to investigate their biosynthesis and secretion. These studies will be correlated with composition and function of stratum corneum in order to elucidate the contribution of lamellar granules to cohesiveness, permeability, and desquamation of the cornified layer. Model systems in which lamellar granules and stratum corneum are pertubed will be assessed for specific aspects of these relationships; eg. hyperplastic epidermis, essential fatty acid deficiency, and hereditary ichthyosis in the mouse. The results of these studies should help to elucidate the pathogenesis of disorders of keratinization involving defects in permeability and cohesion of stratum corneum such as ichthyosis and psoriasis.